If you're undergoing certain cancer treatments that could cause low blood cell counts, your doctor will likely monitor your blood cell counts regularly using a test called a complete blood count (CBC). Low blood cell counts are detected by examining a blood sample taken from a vein in your arm.

When checking your blood cell count, your doctor is looking at the numbers and types of the following:

White blood cells. These cells help your body fight infection. A low white blood cell count (leukopenia) leaves your body more open to infection. And if an infection does develop, your body may be unable to fight it off.

Red blood cells. Red blood cells carry oxygen throughout your body. Your red blood cells' ability to carry oxygen is measured by the amount of hemoglobin in your blood. If your level of hemoglobin is low, you're anemic and your body works much harder to supply oxygen to your tissues. This can make you feel fatigued and short of breath.

Chemotherapy. Certain chemotherapy drugs can damage your bone marrow — the spongy material found in your bones. Your bone marrow makes blood cells, which grow rapidly, making them very sensitive to the effects of chemotherapy. Chemotherapy kills many of the cells in your bone marrow, but the cells recover with time. Your doctor can tell you whether your specific chemotherapy treatment and dose will put you at risk of low blood cell counts.

Radiation therapy. If you receive radiation therapy to large areas of your body and especially to the large bones that contain the most bone marrow, such as your pelvis, legs and torso, you might experience low levels of red and white blood cells.

Cancers of the blood and bone marrow. Blood and bone marrow cancers, such as leukemia, grow in the bone marrow and don't allow normal blood cells to develop.

Cancers that spread (metastasize). Cancer cells that break off from a tumor can spread to other parts of your body, including your bone marrow. The cancerous cells can displace other cells in your bone marrow, making it difficult for your bone marrow to produce the blood cells your body needs. This is an unusual cause of low blood cell counts.

Low blood cell counts can lead to serious complications that may delay your next round of treatment. Monitoring your blood cell counts allows your doctor to prevent or reduce your risk of complications.

The most serious complications of low blood cell counts include:

Infection. With a low white blood cell count and, in particular, a low level of neutrophils (neutropenia), a type of white blood cell that fights infection, you're at higher risk of developing an infection. And if you develop an infection when you have a low white blood cell count, your body can't protect itself. Infection can lead to death in severe cases.

Even a mild infection can delay your chemotherapy treatment, since your doctor may wait until your infection is cleared and your blood cell counts go back up before you continue. Your doctor may also recommend medication to increase your body's production of white blood cells.

Anemia. A low red blood cell count is anemia. The most common symptoms of anemia are fatigue and shortness of breath. In some cases, fatigue becomes so severe that you must temporarily halt your cancer treatment or reduce the dose you receive.

Anemia can be relieved with a blood transfusion or with medication to increase your body's production of red blood cells.

Bleeding. Low numbers of platelets in your blood can cause bleeding. You might bleed excessively from a small cut or bleed spontaneously from your nose or gums. Dangerous internal bleeding can occur.

A low platelet count can delay your treatment. You may have to wait until your platelet levels go up in order to continue with chemotherapy or to have surgery.

Unless your blood cell counts are very low, you probably won't experience any signs or symptoms and you won't be able to tell that your blood cell counts are down. That's why your doctor may order frequent blood tests to follow your blood cell counts.

Ask your doctor whether your cancer treatment is likely to cause low blood cell counts and what signs and symptoms you should be looking for. If you notice any signs or symptoms of low blood cell counts, tell your doctor right away.

Condition

What to look for

Source: National Cancer Institute, 2011

Low white blood cell count

Fever higher than 100.5 F (38 C)

Chills

Sweating

Low red blood cell count

Fatigue

Chest pain

Dizziness

Shortness of breath

Low platelet count

Bleeding

Easy bruising

Heavy menstrual bleeding

If you have low blood cell counts, your treatment will depend on which counts are low and what's causing the low numbers. Common treatments include:

Blood transfusions. Transfusions help people with low levels of red blood cells and platelets. In a blood transfusion you're given either red blood cells or platelets from people who've donated blood. Though transfusions of white blood cells are possible, they're reserved for specific, rare situations because of the risk of many complications.

Medications. Your doctor may prescribe medications that stimulate the production of more blood cells. Medications have benefits and risks, so talk to your doctor about the possible side effects of drugs used to boost blood cell counts.

Stopping or delaying treatment. In severe cases you may need to stop your cancer treatment altogether, or delay it until your blood cell counts rise.

The type of treatment you receive will depend on your cancer treatment and your physical condition.

Take steps to keep your body healthy when you have low blood cell counts. For example:

Eat a balanced diet. Your body needs all the vitamins and nutrients it can get to heal itself during and after your treatment. Choose plenty of fruits and vegetables. If treatment complications make eating difficult — for example, if you experience nausea and vomiting or mouth sores — experiment to find foods you can tolerate.

Avoid injury. Many everyday activities put you at risk of cuts and scrapes. A low platelet count makes even minor abrasions serious. A low white blood cell count can turn a small cut into a starting point for a serious infection. Use an electric shaver rather than a razor to avoid nicks. Ask someone else to cut up food in the kitchen. Be gentle when brushing your teeth and blowing your nose.

Avoid germs. Avoid unnecessary exposure to germs when you can. Wash your hands frequently or use a liquid hand sanitizer. Avoid people who are sick and stay away from crowds. Have someone else clean the litter box, bird cage or fish tank. Don't eat raw meat or eggs.

Rest. If you feel tired, stop and rest. Your body is working hard to fight the cancer cells and heal the healthy cells damaged by your treatment. Don't feel guilty about taking time for yourself and asking others to help you. Plan your most important activities for the time of day when you feel most energetic.

Talk to your health care team about other ways you can cope with low blood cell counts.

References

Chemotherapy and you: Support for people with cancer. National Cancer Institute. https://www.cancer.gov/publications/patient-education/chemo-and-you. Accessed July 9, 2017.

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